If you were able to go 29 years without any issues, that is FANTASTIC. Not something I would recommend to anyone though.
Corrosion can and often does occur inside these components and internal leaks can develop. Gear oil coolers can fail and dump all of the transmission oil and fill the tranny with seawater. Saltwater can leak into the coolant (engine) side of the system doing internal engine damage, etc. A leaking aftercooler can send seawater spray (or more) into the intake side of the engine causing huge damage over time. Or, these problems can just lead to an overheat, and that alone can cause major damage.
Personally, for a few hours of my time and a few dollars, I would regularly take these components apart, replace seals, O rings, etc., properly clean (the air side of the aftercooler can only be cleaned when taken apart), and pressure test to ensure that my system works and continues to work trouble free.
Tony Athens has photos of many failed components (failed) due to owner neglect, resulting in major expenses that could have been avoided.
Again, good on you that it worked out well. Maybe the components used by CAT are just really good, well engineered, quality products???